Warning: The firmware on the flight controller has been tested and flashed by the factory using USB manually. Not every firmware (especially new firmware which has not been tested by factory) is compatible with the hardware. So we are not responsible if the board is not working after you flash your own firmware onto the board. You are recommended to use the default firmware shipped with the board because it has been tested. Thank you for your kind understanding.

Betaflight Configurator GUI was used by factory (they did not use command line).